welcome to the antenna summit sponsored by nadxa northern
TRANSCRIPT
Welcome to the Antenna Summit
Sponsored by NADXA
Northern Arizona DX Association
1
Thank You
NAU – Cline Library
2
Session 6 – ARRL Antenna Book
Chapter 1 - Antenna Fundamentals
3
Instructor
• Ron Gerlak
• KG7OH – Amateur Extra Class
• Licensed 1977
• ARRL ANTENNA BOOK 24th Edition 2019
• Q & A at the end of each chapter
• Via Chat
• Email questions to: [email protected] - Anytime
4
Radio System
5
Radio Puzzle
Transmitter, Receiver and Antenna System
Get a Signal from Your Transmitter to The other hams Antenna
Propose of AntennasRadiate and receive electrometric
wavesReciprocityAlways & Never
Dissipated Electromagnetic Waves
6
Radiated as Heat 😩
Antennas close to ground
Antennas made of very small wire
Reducing Losses = Increased Radiation Efficiency
Dissipated Electromagnetic Waves
Radiation of Electrometric Waves 😀
ANTENNAS
7
H = Magnetic Field
E = Electrical FieldDetermines Polarization
Electromagnetic Waves
Array of Light (Next Generation of Antennas)
Tom Schiller, N6BT
8
ANTENNAS
Anything Works (Tom Schiller, N6BT)
Everything matters
What Matters
9
Directivity
Gain
Take-Off Angle
Type of Ground
Height Above Ground
Near & Far Fields
Free Space
VSWR
Impedance
• Feed Point Impediance
– Self and Mutual Impedance
– Feed Point Impedance is Low where the voltage is low• At the center of a dipole
Impedance
10
• ResonanceAn antenna can be resonant only at one frequencyCurrent and voltage are in phase
Fields
Near Field
11
Far Field
Boundary = D = 2L2/Wavelength
(Within 2 Wavelengths of the Feed Point)
DIPOLE ANTENNA
12
E and H Wave Forms
13
Antenna Voltage and CurrentDistribution
14
15
Measures intensity of sound and power
Decibels
16
So Double the power twice = 1 S-unit
+6dB = +1 S-unit Higher
Power x 2 = +3dB = 3dB Gain
Just add them up or subtract them
Log scale
• From 100 watts to 200 watts = + 3dB.• From 200 watts to 400 watts = +3dB.• 3dB + 3dB = 6 dB = 1 S-unit
S 6
Power – dB – S Units
17
• From 100 watts to 200 watts = + 3dB.• From 200 watts to 400 watts = +3dB.• 3dB + 3dB = 6 dB = 1 S-unit
S 7
Power – dB – S Units
18
• Change from a Dipole to a 3 element Yagi• = + 6 dBd = 1 S-unit• Same transmit result doubling + doubling power• Considerable improvement in receiving
S 6
- or -
19
• Change from a Dipole to a 3 element Yagi• = + 6 dBd = 1 S-unit• Same transmit result doubling + doubling power• 1 S-unit improvement in receiving
S 7
- or -
20
• RF Waves change with time (Electromagnetic)
Fields and Waves
21
E Fields Electric Wave90 Degrees to the H FieldIncreases with VoltageMost Relevant to Ham RadioDescribes the Polarization of an Antenna
H Fields Magnetic WaveIncreases with Current
TYPES of PATTERNS
• 3D Pattern
• Azimuthal Pattern
• Elevation Pattern
22
ISOTROPIC ANTENNA
23
3D ISOTROPIC ANTENNA PATTERN
24
25
ISOTROPIC ANTENNA PATTERN SLICE
Elevation Pattern Azimuthal Pattern
Horizontal Dipole
The dipole is the simplest type of real antenna from a theoretical point of view. Most commonly it consists of two conductors of equal length oriented end-to-end with the feed-line connected between them.
26
27
3D DIPOLE ANTENNA PATTERN
28
3D DIPOLE PATTERN SLICE
DIPOLE PATTERN
29
Horizontal PatternAzimuth Pattern
Vertical Pattern Elevation Pattern
Horizontal Dipole Pattern
3D Pattern
Azimuth PatternIsotropic shown in Red
30
Gain
• Dipole has 2.15 dBi gain over an Isotropic Antenna
• Signal from the ends is redistributed to the broadside
31
Gain
32
Gain is achieved by redistribution of pattern
Where does the gain come from???
Antennas are passive devices and do not generate any “extra” power.
DB Referance• Isotropic antenna as the reference
Dipole has 2.15 dBi Gain
33
Yagi has ≈ 6 dBd GainDipole antenna as the reference
Yagi has ≈ 8.15 dBi Gain(Same antenna)Isotropic antenna as the reference
Tri-Band Yagi 10 – 15 - 20
34
35
YAGI (Gain Antenna) PATTERN(Azimuth)
Azimuth ½ Power Points of a Yagi
0
90
180
270
30 Degrees
-3
-6
-9
0 dB
3 dB Down½ Power Point
36
Beam Width
Q - Quality
• Narrower Beam width = Higher Q
• Higher the Gain = Higher Q
37
More Selectivity
More Directivity
More Gain
Q - Quality
38
Q - Quality
39
Beam Width of Antennas
Transistors
Resonant RLC Circuits
Azimuth ½ Power Points of a Yagi
0
90
180
270
20 Degrees
-3
-6
-9
0 dB
3 dB Down½ Power Point
40
High “Q” Beam Width
Elevation Pattern of a Yagi
0
90
180
270
-3
-6
-9
0 dB
41
Polarization
• Horizontal
• Vertical
• Circular
• Sky-waves
42
Scaling
• ScalingLength, Spacing, Boom & Element Diameter
43
ERP & EIRP (EiRP)Effective Radiated Power
• TPO = 100 watts = 50 dBm
• Transmission line attenuation = 2.4 dB
• Losses in RF connectors and coupling = 1.7dB
• Antenna gain = 7.5 dBi
• EIRP = 50 dBm – 2.4 dB – 1.7 dB + 7.5 dB =
53.4 dBm = 219 watts
44
Safety
• Thermal Effects
• Athermal Effects
• Radiation
• Power Density
• Safe Levels
• Pacemakers
45
Thermal Effects of RF
Microwave cooks using RF Energy
46
Body’s Natural Resonant Frequency35 MHz – Grounded70 MHz - Insulated from ground
SAR – Specific Absorption Rate
MPE – Maximum Permissible Exposure
Athermal Effects of EMRElectromagnetic Radiation
Electromagnetic FieldEnergy Fields – At Home/Work
– Electric Drill, 500 – 2000 milligauss
– Hair Dryer, 200 – 2000 milligauss
– Electric Blanket, 30 – 90 milligauss
– HF Transceiver , 10 – 100 milligauss
47
More studies – No association
Some studies – Weak association EMF & Malignant Conditions
Radiation
Ionizing – Always a danger
– X Rays
– Gamma Rays
– Nuclear Power
48
Non-Ionizing – Sometimes a ConcernRF Field60 Hz Field
Power Density
Scientific community disagree on guidelines
49
Measurement equipment is expensive
ARRL RF Awareness Guidelines Page 1.24, Table 1.3
ARRL RF Awareness Guidelines
• Keep people away from antennas
• Keep mobile power to < 25 watts
• Make antenna heights > 35’
• Keep equipment covers installed
• Don’t point directional antennas toward people
• Use a speaker microphones with HT radios
• Keep a distance from transformers & fans
50
Safe Exposure LevelsSTATIONS MUST BE EVALUATED
• Controlled Environments
• Uncontrolled Environments
• E Field
• H Field
• Different Frequencies
• Time Period Averaging
51
Experts Do Not Agree
Safe Exposure LevelsNO EVALUATIONS REQUIRED
• 100 maximum watts okay an all Bands except:
• 50 watts or less on:
12 Meters
10 Meters
VHF
UHF
(Table B, Page 1.21)
52
Pacemakers
• DISCUSS THIS WITH YOUR PHYSICIAN!
53
Session 6 – ARRL Antenna Book
Chapter 2 - Dipoles and Monopoles
54
Dipoles and Monopoles
• Effects of Conductor Diameter
• Radiation Patterns and Effects of Ground
• Feed Point Impedance
• Effects of Frequency on Radiation Pattern
• Folded Dipoles
• Vertical Dipoles
• Off Center Fed (OCF) Dipoles
• Monopoles
• Folded Monopoles55
DIPOLES
• Fundamental Antenna
56
Dipole Length Calculations
λ/2 Dipole Resonant Length (in free space)491.786 / f(in MHz) = Length in Feet
Example of 40 Meter Dipole:491.786 / 7.2 = 68.29’
57
Dipole - K FactorLength Correction for Diameter
Dipole Length Corrected for Diameter of #12 AWG
(.969 - .976) Page 2.2, Figure 2.3
491.786 / 7.2 = 68.29’
.97 x 491.786 / 7.2 = 66.3 Feet
58
Dipole - Velocity Factor
Dipole Length Corrected for Insulated Wire
Reference Material says about .95%
My experience says about .99%
491.786 / 7.2 = 68.29’
.97 x 491.786 / 7.2 = 66.25’
.99 x .97 x 491.786 / 7.2 = 65.60’
59
Dipole – Type of Ground
• Very Poor Soil Ground
• Good Ground
• Salt Water
60
Dipole – Height Factor
Resonant length changes up and down as the height above ground changes.
61
Dipole LengthUSE THIS FORMULA IN THE FIELD
• The book says 468 / f for λ/2• Soooo 234 / f(MHz) = the λ/4 element Length
• Cut it 2 feet longer and wrap it back on itself.
Element length =
234 / f then add 2’ just in case
• 234 / 7.2 = 32.5 Then add 2 = 34.5
62
DIPOLES
• Fundamental Antenna
63
Wrap extra wire here
Wrap extra wire here
Make these the actual calculated length
Dipole Length
• Check SWR dip with Antenna Analyzer
• Adjust as needed:
Lengthen Antenna Lowers Dip Frequency
64
65
Dipole LengthTo lower the dip make the antenna longer
66
Dipole Length
Needs to be more longer
67
Dipole Length
Just the right length
Dipoles Height Above Ground
68
DIPOLES
• Fundamental Antenna
69
Folded Dipole
70
Monopole / Vertical
71
Vertical Dipole
72
OCF Dipole
73
Antenna Voltage and CurrentDistribution
74
Feed Point Impedance
Dipole feed point impedance = 72 Ω
75
Vertical Monopole feed point impedance = 36 Ω
Inverted V feed point impedance = 50 Ω
Folded Dipole feed point impedance = 280 Ω
OCF Dipole feed point impedance = 150 - 300 Ω
Slopped feed point impedance = 80 Ω
Next Session –ARRL ANTENNA BOOK
Chapter 3The Effects of Ground
77